fs#renameSync won't work across partitions or attached storage. This is by design, as rename is paired to the C version of the same method, which isn't able to cross disks either. (See this closed issue for more discussion about rename.)

A solution could be piping a readStream to a writeStream, and then cleaning up the source file.
I'd attach a fix but the trouble is that listening for the end event on the pipe and firing a callback would break the synchronous nature of shelljs.

Ideas?

Great module, by the way. Very helpful!